Elastomer composition, method for producing same and pneumatic tire using same

ABSTRACT

An elastomer composition, having an excellent flexibility and low temperature durability, a method for producing the same and a pneumatic tire using the same are provided. An elastomer composition (C) comprising a matrix of a thermoplastic resin (A), in which a dispersed phase of an elastomer component (B) is finely dispersed to form an island-in-sea structure, wherein volume ratios of the thermoplastic resin (A) and the elastomer component (B) satisfy the following formula (I):
 
φ d/φm&gt;ηd/ηm   (I)
 
wherein φd and ηd, respectively, indicate a volume ratio and a melt viscosity of the elastomer component (B), and φm and ηm, respectively, indicate a volume ratio and a melt viscosity of the thermoplastic resin (A)), a method for producing the same and a pneumatic tire using the same.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending U.S. application Ser. No.12/281,348, filed on Sep. 2, 2008; which is a National Phase ofPCT/JP2007/054618 filed on Mar. 2, 2007; and claims priority toApplication No. 2006-058273 filed in Japan on Mar. 3, 2006; the entirecontents of each of these applications is hereby incorporated byreference.

TECHNICAL FIELD

The present invention relates to an elastomer composition, a method forproducing the same and a pneumatic tire using the same. Morespecifically, it relates to an elastomer composition having an excellentflexibility and low temperature durability, while maintaining thecharacteristics of the resin, a method for producing the same and apneumatic tire using the same.

BACKGROUND ART

A thermoplastic elastomer composition comprising a matrix (i.e., acontinuous phase) of a thermoplastic resin, in which a rubber is finelydispersed (i.e., a dispersed phase) is known. It is known in the artthat an island-in-sea structure, in which the rubber is surrounded withthe resin, is formed under the conditions satisfying the formula (IV)explained later (e.g., see Japanese Patent Publication (A) No.2000-159936). To obtain a rubbery elastomer from a composition obtainedin a state where a thermoplastic resin forms a matrix, it is necessaryto increase the amount of rubber as much as possible. However, when alarge amount of rubber is compounded, the thermoplastic resin serving asthe continuous phase and the elastomer component serving as thedispersed phase invert in phase, and, therefore, the thermoplasticelastomer composition thus prepared does not exhibit the fluidity of thethermoplastic resin and the shaping becomes impossible. Therefore, therehave been limits to the amount of rubber which could be compounded.

DISCLOSURE OF THE INVENTION

Accordingly, an object of the present invention is to provide anelastomer composition (C) having a flexible and low temperaturedurability comprising a matrix of a relatively small amount of athermoplastic resin (A), in which a relatively large amount of anelastomer component (B) is finely dispersed, a method for producing thesame and a pneumatic tire using the same.

In accordance with the present invention, there are provided anelastomer composition (C) comprising a matrix of a thermoplastic resin(A), in which a dispersed phase of an elastomer component (B) is finelydispersed to form an island-in-sea structure, wherein volume ratios ofthe thermoplastic resin (A) and the elastomer component (B) satisfy thefollowing formula (I):φd/φm>ηd/ηm  (I)wherein φd and ηd, respectively, indicate a volume ratio and a meltviscosity of the elastomer component (B), and φm and ηm, respectively,indicate a volume ratio and a melt viscosity of the thermoplastic resin(A)) and a pneumatic tire using the same.

In accordance with the present invention, there is further provided amethod for producing the above-mentioned elastomer composition (C)comprising the steps of: mixing and shaping a thermoplastic resin (A),an elastomer component (B) and a plasticizer (D) in a ratio satisfyingthe following formulae (II) and (III):φd/(φm+φ1)×(ηml/ηd)<1  (II)ηml/ηd=0.8-1.2  (III)wherein φd and ηd, respectively, indicate a volume ratio and a viscosityof the elastomer component (B), φm indicates a volume ratio of thethermoplastic resin (A), φl indicates a volume ratio of the plasticizer(D), and ηml indicates a melt viscosity of a mixture of thethermoplastic resin (A) and the plasticizer (D); and, then,

removing the plasticizer (D) by evaporation, extraction or migration.

According to the present invention, it is possible to obtain a flexibleelastic body, while maintaining the properties of the thermoplasticresin, for example, it is possible to prepare an inner liner having acombination of heat resistance, low gas permeability, chemicalresistance and high dynamic durability when using Nylon, as thethermoplastic resin, and using a butyl-based rubber as the elastomer.Due to similar characteristics, it is also possible to use the elasticbody for hose inner liners, packing, etc.

BEST MODE FOR CARRYING OUT THE INVENTION

The inventors engaged in research to solve the above problems and, as aresult, found that, by mixing and shaping a thermoplastic resin (A), anelastomer component (B) and a plasticizer (D) in a compositionsatisfying the above formula (II) to obtain an island-in-sea structure,where the resin (A) forms the sea and the elastomer (B) forms theislands. After the final shape is formed, a part of the composition isremoved, it becomes possible to obtain an island-in-sea structure havinga highly increased ratio of the elastomer more than the limit ordinarilyobtainable, whereby a flexible elastic body due to the high amount ofelastomer, while maintaining the characteristics of the matrixthermoplastic resin (A).

To produce a conventionally known thermoplastic elastomer compositioncomprised of a matrix of a thermoplastic resin component, in which anelastomer component is dispersed (see Japanese Patent Publication (A)No. 9-100413, Japanese Patent Publication (A) No. 2000-159936, etc.),the following conditions are necessary. That is, when a volume ratio ofthe thermoplastic resin component forming the matrix (i.e., continuousphase) is φm, a viscosity at the time of melt mixing is ηm, a volumeratio of the elastomer component forming the dispersed phase is φd, aviscosity under the same conditions is ηd, it is necessary to mix thetwo components so that the value ofα=(φd/φm)×(ηm/ηd)becomes smaller than 1. That is,(φd/φm)×(ηm/ηd)<1  (IV)

This is because, when the microstructure of the thermoplastic elastomercomposition thus produced has the α value of smaller than 1, thethermoplastic resin component becomes the continuous phase (i.e.,matrix) and the elastomer component becomes the dispersed phase (i.e.,domain), and, therefore, molding becomes possible by the molding methodof thermoplastic resins, but when α is 1 or more, the continuous phaseand the dispersed phase are inverted, and, therefore, the thermoplasticelastomer composition thus prepared does not exhibit the fluidity of athermoplastic resin and, therefore, molding by a molding machine forresin becomes possible. Further, when a larger amount of elastomer, ifmore than a certain amount is compounded, the α tends to become largerthan 1 and the continuous phase and the dispersed phase become inverted.There were inherent limits in the conventional known production methodsfor further increasing the elastomer ratio, while maintaining therelationship between the continuous phase comprised of the thermoplasticresin and the dispersed phase comprised of the elastomer.

The present invention provides an elastomer composition, where it ismaintained in such a state that a thermoplastic resin component (A) is acontinuous phase (i.e., matrix) and an elastomer component (B) is adispersed phase (i.e., domain), the volume ratio of the elastomercomponent (B) in the resin is increased to an extent which could not berealized in a conventional production method and a method for producingthe same.

That is, while the elastomer composition (C) satisfies(φd/φm)×(ηm/ηd)>1  (I)a state of a continuous phase (i.e., matrix) of a thermoplastic resincomponent (A), in which an elastomer component (B) is present as adispersed phase (i.e., domain), is formed.

Furthermore, the method for producing the elastomer composition (C) isas follows:

The plasticizer (D) is compounded into the thermoplastic resin component(A) as a pseudo resin component, together with the elastomer component(B), so as to satisfy the following conditions:(φd/(φm+φl))×(ηml/ηd)<1  (II)ηml/ηd=0.8-1.2  (III)wherein φd and ηd, respectively, indicate a volume ratio and a viscosityof the elastomer component (B), φm indicates a volume ratio of thethermoplastic resin (A), φl indicates a volume ratio of the plasticizer(D), and ηml indicates a melt viscosity of a mixture of thethermoplastic resin (A) and the plasticizer (D)).

Due to the above compounding, a thermoplastic elastomer composition (E)comprising a thermoplastic resin component (A) including a plasticizer(D) forming a continuous phase (i.e., matrix) and an elastomer component(B) forming a dispersed phase (i.e., domain) is first produced. Here,the formula (III) shows that, when the viscosity ratio ηml/ηd is madewithin a range of 0.8 to 1.2, it is possible to make the dispersedparticles of the elastomer smaller. It is known in the art that, whenthe dispersed particles is made smaller, the durability is improved (SeeJapanese Patent Publication (A) No. 2000-159936).

Here, φ1/(φm+φ1) is 0.05 to 0.6, more preferably 0.1 to 0.3.

Although the composition (E) thus produced is still of thermoplasticity,the elastomer composition (C) is produced by evaporating, extracting ormigrating the plasticizer (D) from the composition (E). Note that thiselastomer composition (C) loses its thermoplasticity.

As the thermoplastic resin (A) usable for preparation of the elastomercomposition (C) of the present invention, one or more types ofthermoplastic resins may be used. As the resin component,polyamide-based resins (e.g., Nylon 6 (N6), Nylon 66 (N66), Nylon 46(N46), Nylon 11 (N11), Nylon 12 (N12), Nylon 610 (N610), Nylon 612(N612), Nylon 6/66 copolymer (N6/66), Nylon 6/66/610 copolymer(N6/66/610), Nylon MXD6 (MXD6), Nylon 6T, Nylon 6/6T copolymer, Nylon66/PP copolymer, and Nylon 66/PPS copolymer), a polyester-based resin(e.g., aromatic polyesters such as polybutylene terephthalate (PBT),polyethylene terephthalate (PET), polyethylene isophthalate (PEI),PET/PEI copolymer, polyarylate (PAR), polybutylene naphthalate (PBN),liquid crystal polyester, polyoxyalkylene diimidic acid/polybutyleneterephthalate copolymer), polynitrile-based resins (e.g.,polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile/styrenecopolymer (AS), methacrylonitrile/styrene copolymer,methacrylonitrile/styrene/butadiene copolymer), a polymethacrylate-basedresins (e.g., polymethyl methacrylate (PMMA) and polyethylmethacrylate), polyvinyl-based resins (e.g., vinyl acetate (EVA),polyvinyl alcohol (PVA), vinyl alcohol/ethylene copolymer (EVOH),polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), vinylchloride/vinylidene chloride copolymer, and vinylidene chloride/methylacrylate copolymer), cellulose-based resins (e.g., cellulose acetate andcellulose acetobutyrate), fluorine-based resins (e.g., polyvinylidenefluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoroethylene(PCTFE) and tetrafluoroethylene/ethylene copolymer (ETFE)), imide-basedresins (e.g., aromatic polyimide (PI)), etc. may be mentioned. Amongthese, linear polyamide resins such as Nylon are preferably used fromthe viewpoint of obtaining a balance of the durability and the gasbarrier property.

Further, to the thermoplastic resin (A) forming the matrix of theelastomer composition, fillers, reinforcing agents, processing aids,stabilizers, antioxidants, etc. generally used for improving theworkability, dispersability, heat resistance, antioxidation ability,etc. may be compounded, if necessary.

The elastomer component (B) usable for the preparation of the elastomercomposition according to the present invention may be an elastomercomposition comprising an elastomer component, in which the usual rubbercompounding agents including the vulcanization compounding componentshave been compounded. Alternatively, it may be an elastomer compositioncomprising the elastomer component, in which the usual rubbercompounding agents other than the vulcanization compounding componentshave been compounded. As such an elastomer component, natural rubber,synthetic polyisoprene rubber (IR), epoxylated natural rubber,styrene-butadiene rubber (SBR), polybutadiene rubber (BR),nitrile-butadiene rubber (NBR), hydrogenated NBR, hydrogenated SBR, orother such diene-based rubbers and their hydrogenated compounds;ethylene propylene rubber (EPDM, EPM), maleic acid-modifiedethylene-α-olefin copolymer (M-PO), butyl rubber (IIR), isobutylene andaromatic vinyl or diene-based monomer copolymer, acryl rubber (ACM),ionomer, or other such olefin-based rubbers; Br-IIR, Cl-IIR, a bromideof isobutylene paramethylstyrene copolymer (Br-IPMS), chloroprene rubber(CR), hydrin rubber (CHC, CHR), chlorosulfonated polyethylene (CSM),chlorinated polyethylene (CM), maleic acid-modified chlorinatedpolyethylene (M-CM), or other such halogen-containing rubbers;methylvinyl silicone rubber, dimethyl silicone rubber, methylphenylvinylsilicone rubber, or other such silicone rubbers; polysulfide rubber orother such sulfur-containing rubbers; vinylidene fluoride-based rubbers,fluorine-containing vinyl ether-based rubber,tetrafluoroethylene-propylene-based rubber, fluorine-containingsilicone-based rubber, fluorine-containing phosphagen-based rubber orother such fluororubbers; a styrene-based elastomer, olefin-basedelastomer, polyester-based elastomer, urethane-based elastomer,polyamide-based elastomer, or other such thermoplastic elastomer, etc.may be mentioned.

The elastomer component (B) forming the dispersed phase of the elastomercomposition (C) according to the present invention may also bedynamically vulcanized. The vulcanization agent, vulcanization aid andvulcanization conditions (e.g., temperature and time) etc. in the caseof dynamic vulcanization may be appropriately determined depending uponthe composition of the elastomer component (B) added and is notparticularly limited. As the vulcanization agent, general rubbervulcanization agents (e.g., cross-linking agents) may be used.Specifically, as sulfur-based vulcanization agents, powdered sulfurs,precipitated sulfurs, dispersible sulfurs, surface treated sulfurs,insoluble sulfurs, dimorpholine disulfides, alkylphenol sulfides, etc.may be mentioned. For example, about 0.5 to 4 parts by weight (parts byweight per 100 parts by weight of elastomer component (or polymer)) orso may be used.

Further, as an organic peroxide system vulcanization agent, benzoylperoxide, t-butylhydroperoxide, 2,4-dichlorobenzoyl peroxide,2,5-dimethyl-2,5-di(t-butylperoxy)hexane,2,5-dimethylhexane-2,5-di(peroxylbenzoate), etc. may be mentioned. Forexample, about 1 to 20 parts by weight may be used. Furthermore, as thephenol resin-based vulcanization agent, a mixed cross-linking systemcontaining a bromide of an alkylphenol resin, stannous chloride,chloroprene, or another halogen donor and an alkylphenol resin etc. maybe illustrated. For example, about 1 to 20 parts by weight may be used.

As other compounding components, zinc white (about 5 parts by weight),magnesium oxide (about 4 parts by weight), litharge (about 10 to 20parts by weight), p-quinone dioxime, p-dibenzoylquinine oxime,tetrachloro-p-benzoquinone, poly-p-dinitrosobenzene (about 2 to 10 partsby weight), and methylene dianiline (about 0.2 to 10 parts by weight)may be illustrated.

Further, if necessary, a vulcanization accelerator may also be added. Asthe vulcanization accelerator, an aldehyde-ammonia-based,guanidine-based, thiazole-based, sulfonamide-based, thiuram-based,dithio acid salt-based, thiourea-based, or other general vulcanizationaccelerators may be used in an amount of, for example, about 0.5 to 2parts by weight. Further, as the vulcanization acceleration aid, ageneral aid for rubber may be used together. For example, stearic acid,oleic acid, and their Zn salts (about 2 to 4 parts by weight) etc. maybe used.

Furthermore, the elastomer component (B) forming the dispersed phase mayhave suitably compounded, in addition to the above compounding agents, asoftening agent, antioxidant, processing aid, etc. generally compoundedfor improving the dispersability, heat resistance, etc. if necessary.

As the plasticizer (D) usable in the method of production of the presentinvention, alkylbenzene sulfonamide, diallyl phthalate, dioctylphthalate, dioctyl sebacate, dioctyl adipate, diisodecyl phthalate,butylbenzyl phthalate, tricresyl phosphate, trimellitic acid isononylester and other esters, methanol, ethanol, 2-propanol, and otheralcohols, paraffin oil, naphthene oil, aromatic oil, and otherpetroleum-based oils etc. may be used, but from the viewpoints of a highboiling point and solubility with resins, alkylbenzene sulfonamide ispreferable.

In the present invention, the method for producing of an elastomercomposition (C) comprising a matrix resin (A), in which an elastomer (B)is finely dispersed, may, for example, be as follows: First, theelastomer and, if necessary, the compounding agents are compounded, inadvance, using a general kneader, Banbury mixer, etc. until obtaining ahomogeneous mixed state to prepare an elastomer component (B). At thistime, the elastomer component (B) may have suitable amounts of carbonblack, oil, or calcium carbonate or another filler added thereto.Further, in the necessary case, a vulcanization agent or cross-linkingagent of the elastomer, a vulcanization aid, vulcanization accelerator,etc. may also be added. Next, the thermoplastic resin (A) forming thematrix, the plasticizer (D), and the antioxidant or other compoundingagents compounded, if necessary, are charged into a twin-screw kneaderetc. and kneaded to prepare a thermoplastic resin component (A) formingthe matrix. The resin component (A) thus prepared and the elastomercomponent (B) are charged into a twin-screw extruder etc. for meltmixing. When using an elastomer component (B) not containing anyvulcanization compounding agents for the elastomer component (B), thevulcanization compounding agents may be added at the stage wheresufficient mixing has been performed and further mixed to dynamicallycross-link the elastomer component and obtain a thermoplastic elastomercomposition (E).

Further, the various compounding agents may be added to thethermoplastic resin component (A) or elastomer component (B) by mixing,in advance, before the above twin-screw kneading, but may also be addedduring the above twin-screw kneading. Furthermore, the matrix resin,elastomer, various compounding agents and the plasticizer may be kneadedby a twin-screw kneader etc. all at once, but in that case, it isnecessary to sufficiently knead the matrix resin and the plasticizer,then add the elastomer. The kneading of these elastomer component (B)and the matrix resin component (A) and the melt kneading of theelastomer composition should be conducted under the condition of atemperature, at which a thermoplastic resin melts, or more. Further, theshear rate at the time of kneading is preferably 500 to 7500 sec⁻¹,while the kneading time is preferably about 30 seconds to 10 minutes.

The thermoplastic elastomer composition (E) thus obtained is then formedinto a sheet, film or tube, using a T-type sheeting die, a straight orcrosshead structure tubing die, a cylindrical die for inflation molding,etc. at the front end of a single-screw extruder, then a part or all ofthe plasticizer (D) is removed by evaporation with oven heating, bymigration with laminating with rubber, etc, followed by heat pressing,or by extraction using a solvent such as methanol, etc. to therebyobtain the shaped articles of the elastomer composition (C). For theutilization, as a low permeability layer for a pneumatic tire, hose,etc., the above thermoplastic elastomer composition (E) containing aplasticizer is adhered in a laminated state with rubber to, for example,the innermost layer of a tire or hose, the resultant assembly is formedinto the final shape, then heat pressing is used to move the plasticizer(D) into the rubber so as to obtain a low permeability layer formed fromthe elastomer composition (C). This layer is composed of a resin as amatrix and rubber as a dispersed phase, with an extremely large amountof rubber and, therefor, becomes a flexible layer having a superiordynamic endurance like rubber, while maintaining the characteristics ofthe resin, for example, the low permeability, heat resistance andchemical resistance.

EXAMPLES

Examples will now be used to further illustrate the present invention,but the present invention is by no means limited in scope by theseExamples.

Examples 1 to 7 and Comparative Examples 1 to 7

Preparation of Samples

In each formulation shown in Table I, the elastomer and cross-linkingagent were mixed in an internal-type Banbury mixer (made by Kobe SteelCorporation) at 100° C. for 2 minutes to prepare a compound, which wasthen pelletized by a rubber pelletizer (made by Moriyama ManufacturingCo., Ltd.). Into the resin pellets, a plasticizer for resin (i.e. butylbenzene sulfonamide BM-4 made by Daihachi Chemical Industry Co., Ltd.)was added to about 30% by weight, based upon the weight of the resin(φ1/(φm+φ1)=0.26) and kneaded by a twin-screw type kneader (made byJapan Steel Works), then the plasticizer-containing resin thus obtainedand the rubber pellets were kneaded again by a twin-screw type kneader(made by Japan Steel Works) to prepare pellets of aplasticizer-containing elastomer composition, which was dynamicallyvulcanized. The pellets thus prepared were formed into a sheet by aT-die molding machine, the plasticizer was removed by extraction usingmethanol, then the sheet was dried in a vacuum oven at 70° C. for 12hours to completely remove the methanol, whereby a sheet of theelastomer composition was obtained.

Example 8

In the formulation shown in Table I, the elastomer and the cross-linkingagent were mixed in an internal-type Banbury mixer (made by Kobe SteelCorporation) at 100° C. for 2 minutes to prepare an elastomercomposition, which was then pelletized by a rubber pelletizer (MoriyamaManufacturing Co., Ltd.). Into the resin pellets, a plasticizer forresin (butyl benzene sulfonamide BM-4 made by Daihachi Chemical IndustryCo., Ltd.) was added to about 30% by weight, based upon the weight ofthe resin and kneaded by a twin-screw kneader (made by Japan SteelWorks), then the plasticizer-containing resin obtained and the elastomerpellets were kneaded again by a twin-screw-type kneader (made by JapanSteel Works) to prepare pellets of a plasticizer-containing elastomercomposition, which was (dynamically vulcanized. The pellets preparedwere formed into a sheet by a T-die molding machine, which was thendried in a vacuum oven at 180° C. for 30 hours to evaporate off theplasticizer, whereby a sheet of the elastomer composition was obtained.

Example 9

In the formulation shown in Table I, the elastomer and the cross-linkingagent were mixed in an internal-type Banbury mixer (made by Kobe SteelCorporation) at 100° C. for 2 minutes to prepare an elastomercomposition, which was the pelletized by a rubber pelletizer (MoriyamaManufacturing Co., Ltd.). Into the resin pellets, a plasticizer forresin (butyl benzene sulfonamide BM-4 made by Daihachi Chemical IndustryCo., Ltd.) was added to about 30% by weight, based upon the weight ofthe resin and kneaded by a twin-screw kneader (made by Japan SteelWorks), then the plasticizer-containing resin obtained and the elastomerpellets were kneaded again by a twin-screw kneader (made by Japan SteelWorks) to prepare pellets of a plasticizer-containing elastomercomposition, which was dynamically vulcanized. The pellets prepared wereformed into a sheet by a T-die molding machine, which was thensandwiched between 2 mm sheets of a rubber compound having the followingcomposition and then heat pressed at 180° C. for 15 minutes to evaporatethe plasticizer, whereby the plasticizer is migrated to the rubbercompound to thereby obtain a sheet of the elastomer composition.

Composition of Rubber Compound

Component Parts by weight Manufacturer/Grade Natural rubber 80 RSS#1SBR1502 20 Nippon Zeon/Nipole 1502 FEF carbon black 50 ChubuCarbon/HTC100 Stearic acid 2 Kao/Lunac YA Zinc oxide 3 Seido ChemicalIndustrial/ Zinc White No. 3 Sulfur 3 Karuizawa Refinery/ PowderedSulfur Vulcanization 1 Ouchi Shinko Chemical accelerator Industriesnoccelar NS-P Aromatic oil 2 Nippon Petrolecim/Coumorex 300

The sheets obtained were determined for physical properties by thefollowing test methods. The results are shown in Table I.

Test Methods for Evaluation of Physical Properties

Air permeability: According to JIS K 7126 “Test Method for GasPermeability of Plastic Film and Sheet (Method A)”

Test piece: A film sample prepared in each Example was used

Test gas: air (N₂:O₂=8:2)

Test temperature: 30° C.

To maintain the air pressure, 20×10⁻¹² (cm³·cm/cm²·sec·cmHg) or less isgood, while 15×10⁻¹² (cm³·cm/cm²·sec·cmHg) or less is preferable.

M50 (−20° C.): Determined according to JIS K6251 at −20° C.

Dynamic Fatigue (−20° C.)

Constant strain test at −20° C.: A JIS No. 3 dumbbell was used to applyrepeated strain of 40% by a constant strain tester (made by UeshimaSeisakusho Works) at −20° C. or less. Samples with points of 70%breakage rates by a Weibull plot exceeding 1 million cycles were judgedas passing.

TABLE I Formulation (parts by weight) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex.6 Ex. 7 Ex. 8 Ex. 9 Elastomer IPMS*¹ 100 100 100 90 80 70 — 70 80Mah-EPM*² — — — 10 — — 40 — 10 Br-IIR*³ — — — — 20 — — — — IIR*⁴ — — — —— 30 — — 10 PIB*⁵ — — — — — — 60 30 — Cross-linking ZnO*⁶ 1.0 1.0 1.01.0 1.0 1.0 1.0 1.0 1.0 agent Stearic acid*⁷ 0.5 0.5 0.5 0.5 0.5 0.5 0.50.5 0.5 Thermoplastic Nylon 6.66*⁸ 56 — — 60 67 67 60 56 42 resin Nylon6*⁹ — 53 — — — — — — — Nylon 11*¹⁰ — — 53 — — — — — 25 (Total) (157.5)(154.5) (154.5) (161.5) (168.5) (168.5) (161.5) (157.5) (168.5)(φd/(φm + φl)) × (at kneading, 0.92 0.85 0.89 0.90 0.95 0.95 0.76 0.800.93 (ηml/ηd) with plasticizer) (φd/φm) × (shaped 5.61 5.98 2.20 5.505.76 5.76 4.63 4.87 3.66 (ηm/ηd) article, no plasticizer) Airpermeability × 10⁻¹² 8 6 12 8 9 8 7 7 9 (cm³ · cm/cm² · sec · cmHg)M50(−20° C.) (MPa) 19 22 17 21 24 23 22 21 19 Dynamic fatigue (−20° C.)Good Good Good Good Good Good Good Good Good Comp. Comp. Comp. Comp.Comp. Comp. Comp. Formulation (parts by weight) Ex. 1 Ex. 2 Ex. 3 Ex. 4Ex. 5 Ex. 6 Ex. 7 Elastomer IPMS*¹ 100 100 100 90 80 70 70 Mah-EPM*² — —— 10 — — — Br-IIR*³ — — — — 20 — — IIR*⁴ — — — — — 30 — PIB*⁵ — — — — —— 30 Cross-linking ZnO*⁶ 1.0 1.0 1.0 1.0 1.0 1.0 1.0 agent Stearicacid*⁷ 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Resin Nylon 6.66*⁸ 250 — — 260 320320 200 Nylon 6*⁹ — 250 — — — — — Nylon 11*¹⁰ — — 110 — — — — (Total)(351.5) (351.5) (211.5) (361.5) (421.5) (421.5) (301.5) (φd/(φm + φl)) ×(at kneading) 0.26 0.23 0.50 0.26 0.25 0.25 0.26 (ηml/ηd) (φd/φm) ×(Shaped 0.98 0.98 0.97 0.98 0.94 0.94 0.98 (ηm/ηd) article) Airpermeability × 10⁻¹² 4 2 10 4 5 3 4 (cm³ · cm/cm² · sec · cmHg) M50(−20° C.) (MPa) 48 51 25 46 46 50 41 Dynamic fatigue (−20° C.) Poor PoorPoor Poor Poor Poor Poor Notes of Table I *¹IPMS (Exxon89-4) (viscosity:200 Pa · s) made by Exxon Mobile Chemicals *²Mah-EPM (Tufmar MP0620)(viscosity: 120 Pa · s) made by Mitsui Chemicals *³Br-IIR (BromobutylX2) (viscosity: 20 Pa · s) made by Bayer *⁴IIR (Exxon Butyl 268)(viscosity: 80 Pa · s) made by Exxon Mobile Chemicals *⁵PIB (OppanolB100) (viscosity: 300 Pa · s) made by BASF *⁶Zinc white (Zinc No. 3)made by Seido Chemical Industries *⁷Stearic acid (Beads Stearic Acid)made by NOF Corporation *⁸Nylon 6.66 (UbeNylon 5033B) (viscosity: 500 Pa· s) made by Ube Industries *⁹Nylon 6 (UbeNylon 1030B) (viscosity: 500Pa · s) made by Ube Industries *¹⁰Nylon 11 (Rilsan BESNOTL) (viscosity:200 Pa · s) made by ARKEMA

Viscosity of Plasticizer-Containing Nylon

Plasticizer-containing Nylon 11: 150 Pa·s

Plasticizer-containing Nylon 6: 170 Pa·s

Plasticizer-containing Nylon 6,66: 200 Pa·s

Comparative Examples 8 to 13

Each elastomer and the cross-linking agent were mixed by aninternal-type Banbury mixer (made by Kobe Steel Corporation) at 100° C.for 2 minutes to prepare a compound, which was then pelletized by arubber pelletizer (made by Moriyama Seisakusho). Pellets of the compoundand the pellets of the resin were kneaded by a twin screw kneader (madeby Japan Steel Works). A part thereof was inverted in phase and couldnot be kneaded due to the fact that the rubber ratio is too high. Thepellets prepared were formed into sheets by a T-die molding machine toobtain sheets of a thermoplastic elastomer composition. The sheetsobtained were determined for physical properties as explained above. Theresults are shown in Table II.

TABLE II Comp. Comp. Comp. Comp. Comp. Comp. Formulation (parts byweight) Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Elastomer IPMS*¹ 100 100100 100 100 100 Cross-linking ZnO*¹ 1.0 1.0 1.0 1.0 1.0 1.0 agentStearic acid*¹ 0.5 0.5 0.5 0.5 0.5 0.5 Resin Nylon 6.66*¹ 250 — — 60 — —Nylon 6*¹ — 250 — — 60 — Nylon 11*¹ — — 110 — — 60 (Total) 351.5 351.5211.5 161.5 161.5 161.5 (φd/φm) × (shaped article, 0.98 0.98 0.97 4.104.10 1.78 (ηm/ηd) no liquid) State — — — Phase Phase Phase inversion,inversion, inversion, poor poor poor Air permeability × 10⁻¹² 4 2 11 NotNot Not (cm³ · cm/cm² · sec · cmHg) measurable measurable measurableM50(−20° C.) (MPa) 50 51 28 Not Not Not Dynamic fatigue (−20° C.) PoorPoor Poor measurable measurable measurable ^(*1)See the notes of Table I

Comparative Examples 14 to 16

Each elastomer and cross-linking agent were mixed by an internal-typeBanbury mixer (made by Kobe Steel Corporation) at 100° C. for 2 minutesto prepare a compound, which was then pelletized by a rubber pelletizer(made by Moriyama Seisakusho). Into the resin pellets, a plasticizer forresin (butyl benzene sulfonamide BM-4 made by Daihachi Chemical IndustryCo., Ltd.) was added in an amount of about 30% by weight based upon theweight of the resin and kneaded by a twin-screw kneader (made by JapanSteel Works), then the plasticizer-containing resin obtained and therubber pellets were kneaded again by a twin-screw kneader (made by JapanSteel Works) to prepare pellets of a plasticizer-containing elastomercomposition. The pellets prepared were formed into sheets by a T-diemolding machine to obtain sheets of a thermoplastic elastomercomposition. The sheets obtained were measured for physical propertiesas explained above. The results are shown in Table III.

TABLE III Comp. Comp. Comp. Formulation (parts by weight) Ex. 14 Ex. 15Ex. 16 Elastomer IPMS*¹ 100 100 100 Cross-linking agent ZnO*¹ 1.0 1.01.0 Stearic acid*¹ 0.5 0.5 0.5 Resin Nylon 6.66*¹ 56 — — Nylon 6*¹ — 53— Nylon 11*¹ — — 53 Plasticizer*² 24 22 22 (Total) 181.5 176.5 176.5(φd/(φm + φl)) × (at kneading 0.92 0.85 0.89 (ηml/ηd) and shapedarticle, with plasticizer) Air permeability × 10⁻¹² 26 25 35 (cm³ ·cm/cm² · sec · cmHg) M50(−20° C.) (MPa) 15 16 12 Dynamic fatigue (−20°C.) Good Good Good *¹See notes of Table I *²Butylbenzene sulfonamide(BM-4 made by Daihachi Chemical Industry Co., Ltd.)

Tire Tests

The sheets obtained were used for the following tire tests. The resultsare shown in Table IV.

TABLE IV Comp. Comp. Comp. Ex. 1 Ex. 3 Ex. 1 Ex. 3 Ex. 14 Air leakagePass Pass Pass Pass Fail −20° C. dynamic Pass Pass Fail Fail Passdurability test

Air leakage test: The material described in each Example (thickness 0.15mm) was used as an inner liner to prepare a 195/65/R15 size tire. Thechange in internal pressure at an initial air pressure of 250 KPa and a25° C. atmosphere was measured over three months. The tire was comparedwith a tire using a standard inner liner of butyl rubber/natural rubber80/20% by weight. A tire with at least the same retention rate ofinternal pressure was judged as passing, while one with less was judgedas failing.

−20° C. Dynamic durability test: The material described in each example(thickness 0.15 mm) was used for an inner liner to prepare a 195/65/R15size tire. This was run under conditions of an air pressure of 120 KPaand a −20° C. atmosphere under a load of 4.8 kN on a metal drum for30,000 km. Thereafter, the inner liner was observed. Samples wherecracks occurred were judged as failing.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to obtain a flexibleelastic body, while maintaining the characteristics of the thermoplasticresins, and, therefore, for example, it is possible to prepare an innerliner having heat resistance, low gas permeability, chemical resistanceand high dynamic durability and, due to similar properties, it ispossible to use the same for other parts of pneumatic tires, hose innertubes, packing, etc.

The invention claimed is:
 1. A method for producing an elastomercomposition (C) having no thermoplasticity which comprises a matrix of athermoplastic resin (A) in which a dispersed phase of an elastomercomponent (B) is finely dispersed to form an island-in-sea structure,wherein volume ratios of the thermoplastic resin (A) and the elastomercomponent (3) satisfy the following formula (I):φd/φm>ηd/ηm  (I) where φd and ηd, respectively, indicate a volume ratioand a melt viscosity of the elastomer component (B) and φm and ηm,respectively, indicate a volume ratio and a melt viscosity of thethermoplastic resin (A), said method comprising: mixing and shaping athermoplastic resin (A), an elastomer component (B) and a plasticizer(D) in a ratio satisfying the following formulae (II) and (III):φd/(φm+φ1)×(ηn/ηd)<1  (II)ηml/ηd=0.8-1.2  (III) wherein φd and ηd, respectively, indicate a volumeratio and a viscosity of the elastomer component (B), φm indicates avolume ratio of the thermoplastic resin (A), φ1 indicates a volume ratioof the plasticizer (D) and ηml indicates a melt viscosity of a mixtureof the thermoplastic resin (A) and the plasticizer (D); and, then,removing the plasticizer (D) by evaporation, extraction or migration. 2.A method for producing an elastomer composition (C) according to claim1, wherein the plasticizer (D) is alkylbenzene sulfonamide.
 3. A methodas claimed in claim 1, wherein the thermoplastic resin (A) is at leastone thermoplastic resin selected from the group consisting of Nylon 6,Nylon 6/66 copolymer, Nylon 11, Nylon 12, a Nylon 6/10 copolymer and aNylon 6/12 copolymer.
 4. A method as claimed in claim 1, wherein theelastomer component (B) is at least one elastomer selected from thegroup consisting of a bromide of an isoprene-paramethyl styrenecopolymer, a maleic anhydride-modified ethylene-α-olefin copolymer,butyl rubber, halogenated butyl rubber and polyisoprene rubber.